/*
 * Copyright (c) 2011-2019 Contributors to the Eclipse Foundation
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
 * which is available at https://www.apache.org/licenses/LICENSE-2.0.
 *
 * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
 */

package io.vertx.core.impl;

import io.netty.util.concurrent.FastThreadLocalThread;

import java.util.concurrent.TimeUnit;

/**
 * 允许获得当前的 Context
 * 
 * @author <a href="mailto:nmaurer@redhat.com">Norman Maurer</a>
 */
public final class VertxThread extends FastThreadLocalThread implements BlockedThreadChecker.Task {

	static final String DISABLE_TCCL_PROP_NAME = "vertx.disableTCCL";
	static final boolean DISABLE_TCCL = Boolean.getBoolean(DISABLE_TCCL_PROP_NAME);

	private final boolean worker;
	private final long maxExecTime;
	private final TimeUnit maxExecTimeUnit;
	private long execStart;
	private ContextInternal context;

	public VertxThread(Runnable target, String name, boolean worker, long maxExecTime, TimeUnit maxExecTimeUnit) {
		super(target, name);
		this.worker = worker;
		this.maxExecTime = maxExecTime;
		this.maxExecTimeUnit = maxExecTimeUnit;
	}

	/**
	 * @return the current context of this thread, this method must be called from
	 *         the current thread
	 */
	public ContextInternal getContext() {
		return context;
	}

	/**
	 * @return the current context of this thread, this method must be called from
	 *         the current thread
	 */
	public ContextInternal context() {
		return context;
	}

	private void executeStart() {
		if (context == null) {
			execStart = System.nanoTime();
		}
	}

	private void executeEnd() {
		if (context == null) {
			execStart = 0;
		}
	}

	public long startTime() {
		return execStart;
	}

	public boolean isWorker() {
		return worker;
	}

	@Override
	public long maxExecTime() {
		return maxExecTime;
	}

	@Override
	public TimeUnit maxExecTimeUnit() {
		return maxExecTimeUnit;
	}

	/**
	 * Begin the emission of a context event.
	 * <p>
	 * This is a low level interface that should not be used, instead
	 * {@link ContextInternal#dispatch(Object, io.vertx.core.Handler)} shall be
	 * used.
	 *
	 * @param context the context on which the event is emitted on
	 * @return the current context that shall be restored
	 */
	ContextInternal beginEmission(ContextInternal context) {
		if (!ContextImpl.DISABLE_TIMINGS) {
			executeStart();
		}
		ContextInternal prev = this.context;
		this.context = context;
		return prev;
	}

	/**
	 * End the emission of a context task.
	 * <p>
	 * This is a low level interface that should not be used, instead
	 * {@link ContextInternal#dispatch(Object, io.vertx.core.Handler)} shall be
	 * used.
	 *
	 * @param prev the previous context thread to restore, might be {@code null}
	 */
	void endEmission(ContextInternal prev) {
		// We don't unset the context after execution - this is done later when the
		// context is closed via
		// VertxThreadFactory
		context = prev;
		if (!ContextImpl.DISABLE_TIMINGS) {
			executeEnd();
		}
	}
}
